Friday, September 28, 2012

LiFePO4 ESS Update - Daytime Charging OK for a week now

Starting last saturday, I now have been charging and discharging my LiFePO4 ESS for almost a full week

Saturday = Charging all day

Sunday = Discharging all day (with some pauses)

On Monday, I set up a timer to start and stop the charger automatically and leave it all day long while at work 

Starting on a timer at 07:30, the batteries are slowly charging (@ 10A) at home, during the day, until the charge is cut off at 17:40 to simulate the daytime charging it will do with the solar system in the future

Using Karotz as a webcam, I can watch my meters from work while or on my iPhone from anywhere

Arriving home, here is the situation: we are at the very end of the charge, the charger is pushing 1A only into the batteries and voltage showing 29V, the cut off is very near

Lowest capacity cells groups shwoing 3.93V and 3.91V are fine, and probably did not reach 4V

Total energy used to charge on monday = 3.3 kWh

Charger is pushing 1A only into the batteries and voltage showing 29V, the cut off is very near

and charger end of charge cut off has now happened: Ampmeter is reading 0A and voltage is slowly dropping from 29V

Charger LED2 is now green, meaning the charge is over (and it will not start again unless the AC side is cut off for 10 seconds, it is a security feature)

Wattson Pro graph for Monday: Charging 07:30-18:40 & Discharging 18:40-22:30 
The blue line represents the production from the BESPSS and is almost perfectly matching the usage (in red), unless too high (production maximum output is 1000W for now)

Tuesday: Charging 07:30-17:40 & Discharging 17:40-22:30

After that I moved Karotz to see the Ampmeter too

Reaching the end of the charge: Ampmeter showing 5A (half and going down) and voltage 28.6V

Timer cut off => Ampmeter is showing 0A and voltage is dropping

Wednesday: Charging 07:30-17:40 & Discharging 17:40-22:30



Thursday: Charging 07:30-17:40 & Discharging 17:40-auto cut off at 22:45

Overall I am very satisfied with this week of tests:

 - Charger work fine (long periods of charge and automatic cut off at the end of charge) and the batteries are now well balanced (no group of cells is going too high)

- Automated power output from the BESPSS is matching the home usage (as much as possible) and automatic cut off is working fine, protecting the battery bank from going to low in voltage

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